1. Field of the Invention
The present invention relates to an improvement in an electrical junction system of the type which has a multiplicity of branching lines constituted by laying bus bars and that is adapted for use in connecting electric lines in a wiring harness to constitute a branching circuit arrangement.
2. Description of the Prior Art
In general, a wiring harness used for internal electric wiring in automobiles requires a large number of branching circuits at an intermediate portion thereof. To cope with this demand, a known electrical junction system has been used in which the branching lines corresponding to the branching circuits of the wiring harness are concentrated to a wiring board by means of a bus bar so that the desired electric circuit arrangement is built up in a concentrating manner by connecting the lines of the wiring harness to the branching line on the wiring board.
For instance, in an electrical junction system proposed hitherto, electronic circuits incorporating various relays having different functions such as an intermittent wiper relay, a fuel cut-off relay and so forth are formed in respective branching circuits. More specifically, control elements constituting each branching circuit, e.g. relays, capacitors, diodes and so forth are contained by an independent casing which is connected to suitable portion of the conductive part of bus bar through tab-like terminals provided on the casing.
In recent years, there is a tendency of upgrading of automobiles which in turn increases the number of electric devices used on the automobile, as well as higher quality and diversification of function of each electric device. On the other hand, there is an increasing demand for the improvement in the safety, driveability and comfort of automobiles. These demands naturally increase the number of the branching circuits in the wiring harness, as well as causing a remarkable increase in the diversification and number of electronic parts incorporated in each branching circuit.
The adoption of an electrical junction system of the relay unit type, therefore, encounters the following problems. Namely, the size of the electrical junction system of the relay unit type is inevitably increased to require a larger installation space which is difficult to find. The size increase is partly because of the increase in the number of relay units and partly because of the increased sizes of the relay units themselves. Another problem is that the productivity of the wiring harness is lowered due to the complication in the construction of the wire harness.